This application is directed to an electrical transfer switch and, more particularly, to an electrical transfer switch mountable in a standard electrical panel and having an internal interlock.
Typically, a transfer switch assembly is used to connect an auxiliary power supply with certain electrical circuits in a building. The transfer switch assembly includes a first input switch engaged with electrical conductors connected to the utility supply and a second input switch engaged with electrical conductors connected to the auxiliary power supply. In order to prevent both input switches from being ON simultaneously, either the housing of the transfer switch assembly or an external interlock device is typically configured to provide a mechanical interference between the two input switches. The mechanical interference may be, for example, a rigid device directly coupled between the switch arms of the switches or a plate slidably mounted to the housing such that only one of the input switches at a time may be in the ON position to connect an electrical power supply to the electrical system.
A transfer switch assembly typically includes a separate sub-panel, requiring additional installation cost and space. Optionally, an input switch for the auxiliary power supply may be added to a standard electrical panel; however, due to the many sizes and arrangements of electrical panels, a mechanical interlock must then be specially configured between the utility input switch and the auxiliary input switch. Thus, it would be desirable to provide a single input switch mountable in a standard electrical panel which selectively connects either the utility supply or the auxiliary supply to a building's electrical load. Further, if use of a sub-panel is advantageous due to the application requirements, the input switch is similarly mountable in any standard electrical panel configured to fit within the sub-panel.